This invention relates generally to a bidirectional cable television (“CATV”) network that provides services to a user, and more specifically, it relates to reducing noise ingress resulting from electrical/electromagnetic signals entering the CATV network through improperly terminated tap and splitter ports.
The CATV industry has evolved into a provider of many services. These services not only include traditional analog television programming, but also data services that include, digital television programming, internet services, home security services, voice over internet (VOIP) services, pay-per-view monitoring/billing, and others yet to be discovered. All of these services are provided by transferring alternating electrical current signals (“signals”) to and from a user's facility, such as a home or business.
The CATV signals are delivered to these users from a head end along feeder cables. A head end is a facility for processing and distributing signals over a CATV network. Normally, the head end facility houses electronic equipment used to receive and re-transmit video and other signals over the local cable infrastructure. The feeder cables extend from the head end and branch off to the user's facility at a tap having one or more ports. A drop cable, which is a single coaxial cable, is then passed from one of these ports to a user subsystem on or in the user's facility.
At a time when televisions were considered a luxury and when the cable television industry only provided television services, the drop cable may have run directly into one room of the facility to provide signals to one television. In other words, there may have been no splitters between the user tap and the television. Due to the proliferation of televisions and other user devices that utilize the cable television cables, most user facilities now have at least one splitter that allows the signals to pass from the single drop cable into two or more distribution cables, each distribution cable having its own port on the splitter. Additional splitters may be placed on any of these distribution cables for the addition of more distribution cables. Because even the most technologically advanced homes rarely have a television or other user device for each of these distribution cables and their respective splitter ports, many of these distribution cables and unconnected splitter ports, go unused and unterminated to gather undesirable signals present throughout the home. The term “unterminated port” may be used interchangeably for an unused/unterminated tap port, for an unused/unterminated user port physically located on a splitter, for an unused/unterminated end connector, and for a splitter port that is connected to a distribution cable, which is also unused and not connected to a user device. A distribution cable connected to an unused wall jack located in a separate room of a facility is an example of a distribution cable with an unused/unterminated end connector. This wall jack is an end connector that is essentially an extension of the user port on the splitter.
Each of these unterminated ports can allow electrical/electromagnetic signals to enter the CATV network as ingress noise. The CATV industry has been plagued with ingress noise from each user's facility. Any electrical/electromagnetic signals present in the facility can be passed into any unterminated ports, and hence, the CATV network. These electrical/electromagnetic signals can be inadvertently generated by traditional electrical devices with alternating electrical currents, such as garbage disposals, welders, blower motors, etc. These electrical/electromagnetic signals can also include intentionally generated radio signals transmitted by CB radios, cell phones, personal communicators, wireless telephones, wireless baby monitors, etc. While some of these electrical/electromagnetic signals might be desirable for an intended purpose, none of these signals are desirable if/when they are introduced into the CATV network as ingress noise.
For the purpose of clarity, the term “undesirable signals” is used herein to describe any electrical/electromagnetic signals that are not desired within the CATV network. Thus, undesirable signals can include any signals in the CATV network that are not intentionally provided therein. Similarly, the term “ingress noise” is used herein to describe any undesirable signals present in the CATV network that interfere with desired signals within the CATV network. The term “desired signals” is used herein to describe those signals intended to be present within the CATV network. “Noise ingress” is used to describe the act of the ingress noise entering the CATV network and interfering with desired signals.
As mentioned above, the desired signals are delivered to and are received from the user's facility as desired alternating electrical current signals. Ingress noise, without processing or filtering, for example, interacts with the desired signals to create a resulting signal that may be unfit for use, or unusable, by the user.
Typically, the coaxial cable used in a CATV network is designed to contain the desired signals and protect them from undesirable signals that could cause ingress noise. It accomplishes this goal using an electromagnetic shield that can include a thin, conductive foil, and/or braided conductive metal that surrounds the primary conductor. While the coaxial cable does not protect the desired signals perfectly, on a practical level it generally succeeds.
On the other hand, unterminated ports can often leave the CATV network exposed to ingress noise. A port, like a coaxial cable, has a center conductor and a shielding element. Such ports attach to, or are built into, one end of a shielded signal path, such as a coaxial cable, a tap, or a splitter. Any time these conductors in such ports exist in an unprotected state, the conductors and/or the ports can be exposed to the undesirable signals that can become ingress noise that alters the desired signal properties.
When a port built into a splitter is properly connected to a coaxial cable, and ultimately a user device (e.g., television, television tuner, modem, VOIP server, etc.), the splitter, the connectors, the coaxial cables, and/or the end device increase the desired signals relative to the undesirable signals by attenuating the undesirable signals at the paths of entry into the CATV network. However, as discussed above, when such a port is unterminated it is also unshielded, so the CATV network is exposed to undesirable signals at the port that can cause noise ingress. Similarly, if a port is connected, but connected improperly, the CATV network may also be exposed to undesirable signals. The term “unterminated port” will be used herein to include those ports that are not connected to a user device or are improperly connected to a user device.
As can be imagined, ingress noise can pose a significant and costly problem for the cable industry. When undesirable signals enter the CATV network as ingress noise at an unterminated port, not only are the performance of the tap or splitter affected, but ingress noise can enter and disrupt larger portions of the CATV network. In particular, ingress noise flowing into the CATV network from the user's facility in this manner can accumulate and merge with upstream data created by the user's Internet uploads and created by voice transmissions associated with VOIP, etc., to increase the overall noise level, to decrease the overall ratio of desired signals-to-overall noise, and be transmitted to a head end of the CATV network.
The increased noise levels and decreased signal-to-noise ratios caused by the ingress noise can cause degradation of the transmission quality, and in some cases, it can cause the CATV network to fail in transmission. The ingress noise can also cause problems with downstream signals, such as those for analog television, for instance, by altering electrical signals in a manner that causes picture degradation. Failure of digital signals, such as internet, voice over internet protocol (VOIP) and digital television, can take the form of delays in transmission of internet data (e.g., upload or download), or temporary losses of picture. These failures occur when data packets are received at user devices with errors, causing the data packets to be resent, further causing more traffic and congestion in the CATV network. As can be imagined, diagnosing any of these problems is expensive, and fixing the problems is also expensive once they are identified.
Presently, a solution for reducing ingress noise at ports uses a mating “terminating” connector that is physically attached to an otherwise unterminated port. Attaching the terminating connector to the unterminated port completes a circuit that allows signals to pass. The terminating connector causes a 75 Ohm resistance to be mechanically inserted between the center conductor of a port and a ground. In this way, when a port is disconnected from another connector, the signal is terminated to ground at the port, closing an opportunity for noise ingress. However, problems with this setup can arise. For instance, a port can be connected to a mating coaxial cable so the signal is allowed to flow through it, with no user device attached at the end of the coaxial cable. In this case, undesirable signals can ingress into the CATV network at the unterminated end of the coaxial cable and pass through the port. Alternatively, where a terminating connector is connected improperly (e.g., not fully attached, attached incorrectly, etc.), noise can ingress and a faulty signal can pass.
It would be advantageous to reduce or preventingress noise by appropriately terminating the port when it is improperly connected as well as when it is unconnected.